A resonator is a device that exhibits resonant behavior, that is, it oscillates at some frequencies with greater amplitude than at other frequencies. A resonator usually oscillates at specific frequencies because its properties and dimensions are an integral multiple of the wavelength at those frequencies. Resonators may be used to generate waves of specific frequencies or to select specific frequencies from a signal.
In some applications it is desirable to replace a quartz crystal with a microelectromechanical system (MEMS) resonator. For example, efforts have been made to introduce radio frequency (RF) MEMS devices for timing applications. Compared with quartz crystals, MEMS resonators can provide reduced size as well as improved integration with an oscillator or application specific integrated circuits (ASIC), thereby providing reduced overall system costs.
To meet application specifications, a MEMS resonator device often needs to have several characteristics at the same time. These characteristics can include high frequency stability, low supply voltage, low impedance supporting low power consumption, low phase noise and fast start up behavior. To achieve high compatibility for different applications, it is desired to have a variable resonator frequency that is scalable by design rather than by process change. The performance parameters of the resonators depend on the process concept, such as materials, process stability and to a large extent on the resonator design itself.